In conventional load sensors, a typical electrical sensor generally uses a method of detecting the load by using a pressure sensor, an accelerator sensor or a strain gage, or a method of detecting the load by the use of the modulated intensity of light inside an optical fiber caused by flexural loss and compression loss of the optical fiber.
In the above methods, as the electrical processing circuits and the light sensing and emitting apparatus are complex, or their detection accuracy and noise tolerance are low, there has never been a good solution for providing low-cost, downsized and high-precision sensors.
Because the distortion gauge which detects load by converting changes in sectional area and length of a resistor caused by applying the load to the resistor into change in electric resistance can accurately detect an amount of the load, it is used in various uses such as load cells.
As a typical example, a method of detecting an amount of the distortion of a rigid body in which a thin film is put on the rigid body is described in JP 06-84602 A and JP 08-313371 A.
In addition, a sensor which detects contact at an arbitrary position along a cable is proposed in JP 3354506 B.